Alyssa was a delight to know but initially reserved, said Eric Alburtus, the principal of Central High School in Portage, Mich., the city of about 48,000 people where she grew up. “You had to work to get to know her,” he said. “And it was worth it.”

She excelled in the school’s culinary arts program and was known for her baking. Her reserve fell away whenever she was selling muffins to raise money for the school to buy new equipment for the student kitchen. Alyssa would stroll the school halls with a trolley loaded with baked goods during her free periods, Mr. Alburtus said, selling her creations to fellow students.

“That was her way of connecting with people,” he said.

Grief counselors were at the school Friday to meet with students, Mr. Alburtus said. Alyssa’s culinary instructor could not bear to go to school on the day after her student’s death, Mr. Alburtus said.

The driver of the car, Richard Rojas, 26, has been charged with murder, attempted murder, and aggravated vehicular homicide. He is in police custody.

William Aubry, the assistant police chief in charge of Manhattan South detective squad, said Friday afternoon that Alyssa’s 13-year-old sister was being treated at NewYork-Presbyterian/Weill Cornell Medical Center for a collapsed lung and broken pelvis.

“Our heart goes out to Alyssa, her family and all those that were injured yesterday,” Chief Aubry said.

On Thursday evening, the girls’ father, Thomas Elsman, posted on Facebook that Ava was out of surgery and doing “ok.” He added, “and yes my daughter is gone and I love her so much.”

Ava was one of the people that Alyssa was completely herself around. She is as exuberant as Alyssa was quiet, said their great-grandmother, Clara May Jablonski, 83. “That’s sisterhood,” she said. “They were always close knit.” At home in Michigan, far from where her great-grandchild was killed, Ms. Jablonski worried over how Ava would handle the loss of her sibling, with whom she shared the same long brown hair and striking aqua-colored eyes.

“It makes you want to stay home and hibernate,” Ms. Jablonski said. “Nothing is safe anymore, I’ve come to the conclusion. We’ve had a lot of loss in the family, and to have them go so young is unreal.”

On Friday morning, Ava sent her friend Grace Zak a message via Snapchat, saying she would be out of school for the rest of the year, said Grace’s mother, Kathy.

Alyssa worked as a carhop at the Sonic Drive-In in town, according to her Facebook profile. Her great-grandmother said that holding a job as well as getting an education was a deeply instilled family value.

Their father is the owner of Sporty’s Bar and Grill, in Paw Paw, Mich. They were on the trip to New York with their mother, Jyll Elsman, who is studying to be an accountant, Ms. Zak said.

In pictures on Instagram, Alyssa leans into the arms of her boyfriend, Trevor West. “She motivated me, loved me, gave me everything I needed that I couldn’t give myself,” Mr. West said in an interview with the New York Post on the day she was killed.

“And now that she’s gone, I don’t know how I’m going to fill that void,” he said.

“My son loved this girl fiercely and she brought him joy,” his mother, Stacey Vogl said in a text message on Friday. “Her life was taken much too soon.”